I noticed the same thing.

A few ideas:

* Those spots are the furthest possible distance from the equator (in angular terms), so they should be the most expensive places to put something in orbit (either you launch from a northerly/southerly latitude or spend a lot of fuel on maneuvering into that orbit either way that's expensive)

* Maybe Earth's magnetic field interferes with electronics (less protection from the sun's radiation)

* No one really lives there so there's fewer reasons to spend a lot of money putting something in orbit

* Some kind of international agreement/rules

Maybe someone more knowledgeable could weigh in!